The invention pertains to a device for locking a backrest. The backrest can be folded over a seat portion to allow access to an area behind the backrest.
In known devices of this kind, for example, (DE 196 54 433 C1), using both hands, the backrest is lifted slightly when the locking latches, which are provided at either side of the seat, are disengaged, so that the locking latch cannot fall back into its locking position. Thereafter, in a procedure separate from the unlocking process, the backrest can be folded forward. A protrusion is provided to hold the locking latch in its unlocked position. The protrusion comes to rest, as the latch is pivoted, against a shoulder of the adjustment fitting, which is firmly attached to the seat. The protrusion is held by the weight of the backrest in this position. Due to the fact that wear, which can lead to slippage of the protrusion from the shoulder, can occur between the protrusion and the shoulder, reliable operation of the locking latch decreases with age.
In the case of the known solution, the locking surface and the opposing surface must be configured in wedge-shaped fashion in order to assure that the locking catch falls into place into the corresponding recess on the portion of the fitting that is firmly attached to the seat, and furthermore to assure a lock that is rattle-free. The wedge-shape of these interacting surfaces does have the disadvantage, however, that in certain crash situations, the catch can be moved out of its locking position.
Taking this state of the art as a point of departure, it is the underlying task of the invention to create a device for the locking of a backrest that can be folded and is held rattle-free, and that is not released in the event of a crash.
An apparatus for locking a backrest which is moveable between a folded and an upright position relative to a seat portion is provided. The apparatus comprises a first flanged area attached to the seat portion. A second flanged area is attached to the backrest and is seated on the first flanged area such that the second flanged area is pivotable about a folding axis. A locking latch, articulated on the second flanged area, is moveable between a locked and an unlocked position. In the locked position, a locking surface of the locking latch communicates with an opposing surface on the first flanged area to hold the backrest in place and in the unlocked position the locking surface is disengaged from the opposing surface such that the second flanged area may be pivoted about the folding axis. The pivoting of the second flanged area is limited by a contact surface attached to the backrest and an opposing contact surface on the first flanged area. A handle is provided to move the locking latch between its locked and unlocked positions about a pivot axis which is parallel to the folding axis. A spring element is arranged to move the locking latch about the folding axis when the locking latch is moved into the unlocked position and a readjusting spring biases the locking latch into its locked position.
As a result of a spring propulsion system, which folds the backrest forward, comfort is enhanced to a considerable degree. Due to pre-tensioning from the spring, the backrest of the unoccupied motor vehicle seat is held in place rattle-free. In addition, the locking surfaces, which are free of gradient, exhibit no components of force which would drive the latch from its locking position, so that the closure cannot be released, not even under extreme stress.
A particularly preferred embodiment of the invention includes an additional cam, by means of whose contact surface, which runs eccentric to its axis of pivot, freedom from rattling is further improved. The cam can be moved by the re-adjusting spring of the locking latch. In addition, by means of this cam, the locking latch""s angle of pivot can be limited.